There have been known water cooling, oil cooling, gas cooling, mist cooling and the like as the means for cooling a metal material, which is a heat-treated workpiece, after the heating process thereof.
Among the aforesaid cooling means, the mist cooling is adapted to supply a cooling liquid in a spraying manner through a plurality of nozzles surrounding a heat-treated workpiece so as to cool the treated workpiece by the mist that contains the cooling liquid. The mist means a gas that contains cooling liquid droplets.
A means for measuring the temperature of a heat-treated workpiece has been disclosed in, for example, Patent Literature 1. Further, mist cooling and a means for measuring the temperature of a heat-treated workpiece during mist cooling have been disclosed in, for example, Patent Literatures 2 and 3.
Patent Literature 1 discloses a method in which a temperature sensor (thermocouple) is provided in a dummy specimen having characteristics equivalent to those of a heat-treated workpiece and the temperature of the dummy specimen is measured, thereby managing the temperature of the heat-treated workpiece that is as accurate as the temperature of the heat-treated workpiece directly measured.
Patent Literatures 2 and 3 illustrate a thermocouple provided on a surface of a heat-treated workpiece and a noncontact type temperature measuring instrument, such as a radiation thermometer, as the means for measuring the temperature of a heat-treated workpiece in a mist cooling process.